<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 1987-2017 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation.  A copy of
the license is included in the
section entitled "GNU Free Documentation License".

This manual contains no Invariant Sections.  The Front-Cover Texts are
(a) (see below), and the Back-Cover Texts are (b) (see below).

(a) The FSF's Front-Cover Text is:

A GNU Manual

(b) The FSF's Back-Cover Text is:

You have freedom to copy and modify this GNU Manual, like GNU
     software.  Copies published by the Free Software Foundation raise
     funds for GNU development. -->
<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
<head>
<title>The C Preprocessor: Misnesting</title>

<meta name="description" content="The C Preprocessor: Misnesting">
<meta name="keywords" content="The C Preprocessor: Misnesting">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link href="index.html#Top" rel="start" title="Top">
<link href="Index-of-Directives.html#Index-of-Directives" rel="index" title="Index of Directives">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Macro-Pitfalls.html#Macro-Pitfalls" rel="up" title="Macro Pitfalls">
<link href="Operator-Precedence-Problems.html#Operator-Precedence-Problems" rel="next" title="Operator Precedence Problems">
<link href="Macro-Pitfalls.html#Macro-Pitfalls" rel="prev" title="Macro Pitfalls">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.indentedblock {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
div.smalllisp {margin-left: 3.2em}
kbd {font-style:oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: inherit; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: inherit; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.nocodebreak {white-space:nowrap}
span.nolinebreak {white-space:nowrap}
span.roman {font-family:serif; font-weight:normal}
span.sansserif {font-family:sans-serif; font-weight:normal}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
<a name="Misnesting"></a>
<div class="header">
<p>
Next: <a href="Operator-Precedence-Problems.html#Operator-Precedence-Problems" accesskey="n" rel="next">Operator Precedence Problems</a>, Up: <a href="Macro-Pitfalls.html#Macro-Pitfalls" accesskey="u" rel="up">Macro Pitfalls</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index-of-Directives.html#Index-of-Directives" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Misnesting-1"></a>
<h4 class="subsection">3.10.1 Misnesting</h4>

<p>When a macro is called with arguments, the arguments are substituted
into the macro body and the result is checked, together with the rest of
the input file, for more macro calls.  It is possible to piece together
a macro call coming partially from the macro body and partially from the
arguments.  For example,
</p>
<div class="smallexample">
<pre class="smallexample">#define twice(x) (2*(x))
#define call_with_1(x) x(1)
call_with_1 (twice)
     &rarr; twice(1)
     &rarr; (2*(1))
</pre></div>

<p>Macro definitions do not have to have balanced parentheses.  By writing
an unbalanced open parenthesis in a macro body, it is possible to create
a macro call that begins inside the macro body but ends outside of it.
For example,
</p>
<div class="smallexample">
<pre class="smallexample">#define strange(file) fprintf (file, &quot;%s %d&quot;,
&hellip;
strange(stderr) p, 35)
     &rarr; fprintf (stderr, &quot;%s %d&quot;, p, 35)
</pre></div>

<p>The ability to piece together a macro call can be useful, but the use of
unbalanced open parentheses in a macro body is just confusing, and
should be avoided.
</p>



</body>
</html>
